(Last Updated On: February 18, 2018)

BMI is a very good preliminary measure to assess health risks associated with high body fat. But if your goal is to calculate your Ideal Weight, there are better ways to do that. You will get to know all of them here. Choose what works for you best.

What Is Body Mass Index and is it accurate?

You may have come across this term but never understood it’s significance or real purpose.

BMI stands for Body Mass Index.

Knowing your weight alone doesn’t help as it doesn’t tell you what body fat range you are in. Evaluating your weight against height helps you better estimate your body fat.

Your Body Mass Index can help you determine your fitness and health. It is a good indicator for physicians to assess whether you are at risk of developing any chronic disease.

It helps to estimate whether you are:

  • Under Weight
  • Within Normal Body Weight Range
  • Over Weight, or,
  • Obese

Health risks associated with high BMI

  • Diabetes
  • Heart disease
  • Gallbladder disease
  • Liver Disease
  • Osteoarthritis
  • Sleep Apnea
  • Stroke
  • Cancer

To many of you, it might sound like some scientific jargon. Actually, its a very simple way to estimate your body fat.

1. Calculate BMI yourself

If you know simple maths, you can easily calculate your Body Mass Index. It is your body weight (in kg) divided by 2 times of height in meters.

Calculate BMI using kg and meter (Metric Measurement)

BMI = Your Weight in Kg/ (Height in meters x Height in meters)

Let’s assume your weight is 80 kgs and height is 170 cm (1.7 meters).

BMI = 80/ (170 x 170) = 80/(1.7 x 1.7)= 80/ 2.89 = 27.7

Calculate BMI using Pound and inches (English Measurement

BMI = Your Weight in lbs/ (Height in inches x Height in inches) x 703

For this, let’s assume your weight is 180 lbs and you are 6 feet tall.

Let’s first convert feets to inches.

1 feet = 12 inches
6 feet = 12 x 6 inches = 72 inches

BMI – 180/ (72 x 72) x 703 = (180/ 5184) x 703 = 24.4

Oh.. I am so lost. Is there an easy way to calculate this?

Sure there is. Use the calculator below.

2. BMI Calculator


What is Body Mass Index used for?

  • Body Mass Index helps fitness professionals to co-relate your weight with the amount of body fat.
  • It also helps your nutrition expert to design diet plans based on your current BMI.
  • This simple calculation helps health professionals to discuss weight problems with patients.
I am a healthy individual, why should I care?

It’s important for you to know your Body Mass Index or at least the range.

Unless you know your BMI, you can’t tell whether you are within normal body weight range or not.

When you are overweight, you are at risk of many health disorders.

It doesn’t mean that people with normal BMI will never develop any health disease. However, the possibility of developing a metabolic syndrome increase with the amount of extra body fat you carry. So, it’s important to know whether you are within normal BMI range or not.

Once you know your BMI,  you would need to refer to BMI Chart.

BMI calculation is same for everyone irrespective of age or gender. However, there are different charts for adults and children.

If you are more than 20 years old, you should use the below chart.

BMI chart for Adults

BMI Chart

These reference ranges are defined by World Health Organization (WHO).

Now let’s examine this closely.

  • If your BMI is less than 18.5, you are underweight. This can indicate malnutrition, some eating disorder or an underlining health problem.
  • Body Mass Index between 18.5 and 25 indicates healthy weight.
  • If your BMI is more than 25 but less than 30, you are overweight.
  • People with Body Mass Index of more than 30 are considered obese (severely overweight).

Classes of Obesity

There are different classes of obesity. This helps healthcare professionals to assess health risks associated with obesity.

  • Body Mass Index range of 30-35 is Class I Obesity. This means you have just moved into the obesity zone. If you can take some corrective actions now, you can lower the health risks.
  • Class II Obesity is BMI range of 35-40. If you fall in this zone. You would need to immediately consult a healthcare professional. You would also need to work with a nutrition expert to start losing weight.
  • BMI of more than 40 would put you at an imminent health risk. You would need to consult a healthcare professional immediately.
Note: BMI calculation provides a good estimate of body fat for individuals who are mostly inactive. It cannot be used for assessing the health of athletes and pregnant women. Athletes carry more lean mass and may report higher BMI. Pregnant women usually put on weight during pregnancy and go back to normal BMI post childbirth.

BMI & Fat relation

Health risks associated with Low BMI

Fat in your body is essential for many vital functions in our body. If your BMI is too low, it indicates that your body fat has gone below the minimum amount(essential) needed to sustain. This may lead to:

  • increased bone loss
  • decreased immune function
  • an array of heart problems
  • iron deficiency or anemia

BMI for Children

The same formula can be used to calculate Body Mass Index for children and adolescents below 20 years. But, the interpretation is different and can vary depending on age and gender.

For children, the amount of body fat changes with age. The rate at which fat is accumulated is different for boys and girls. In general, girls between the age 12-16 years carry more fat than boys of the same age.

You would need to compare Body Mass Index of your child against the BMI of other children of the same age. To understand this comparison, you would first need to understand percentile.

A percentile is a measure used in statistics. But don’t worry you wouldn’t have to learn statistics to understand this.

BMI for a group of children of the same age, height, and weight can be plotted on a graph. This can then be divided into multiple zones in terms of increment of a certain percentage (percentiles). Percentile helps to compare your child’s BMI against the rest of the group.

Centers for Disease Control and Prevention (CDC) uses growth charts for children where height (length) and weight is measured against their age. This chart is plotted in percentiles.

If a child has a BMI that puts him/her at or above the 95th percentile, then the child would be considered obese. It means that this child has more body fat than 95 percent of other children in the same age and gender category.

Clinical BMI charts with 5th and 95th percentiles

Birth to 36 Months:

Boys Length-for-age and Weight-for-age Percentiles
Girls Length-for-age and Weight-for-age Percentiles

2 to 20 years:

Boys: Body Mass Index-for-age percentiles
Girls: Body Mass Index-for-age percentiles

Now let’s interpret your child’s BMI in terms of percentile.

  • If your child’s BMI is less than the 5th percentile, then he/she is considered underweight.
  • If the BMI is above the 95th percentile, then your child falls in the obese category.
  • Children with a BMI between the 85th and 95th percentile are considered to be overweight.

Overwhelming? Use the below calculator developed by CDC to determine the percentile of children and teens.

Percentile Calculator for Child and Teen 

Ideal BMI for females is higher than that of Male

There are differing opinions on the definition of underweight in females. Health practitioners quote anything below 18.5 to 20 as underweight for women. Ideal BMI for females should be between 20 to 25.

Is BMI an accurate measure?

BMI was originally designed to estimate body fat in a group of people who lead a sedentary lifestyle.

However, it became widely used to estimate body fat across different societies and people with different lifestyle and activity level.

BMI measurement is a very simple measurement tool for you to estimate your body fat. It’s this simplicity that actually makes this inaccurate.

For instance, Body Mass Index for athletes can be high due to high muscle to fat ratio.

So what’s better than BMI?

While BMI is an effective tool for you to determine whether you are overweight or obese, it’s not the best. Fat around stomach poses more health risks than fat deposits anywhere else.

The fat that you can see and feel when you stretch your skin is called subcutaneous fat. This fat is not all that bad. It helps to regulate your body temperature and protects blood vessels, muscles, and bone.

If you have more fat around your waist, it means that you also have fat deposits around organs. This is called Visceral fat.

Visceral fat collects around organs such as the stomach, intestine, spleen, and kidneys. Fat deposits around your internal organs pose more health risk than fat anywhere else.

Waist Circumference

Waist circumference is a good indicator of visceral fat.

Do this to correctly measure your waist circumference

  1. Take a tailor tape and stand in front of a mirror.
  2. Place the tape measure around your middle, just above your hipbones.
  3. Measure your waist just after you breathe out.

For men, waist circumference in excess of 102 centimeters (40 inches), indicates a higher risk for heart disease and type 2 diabetes.

For women (non-pregnant), the threshold is 88 centimeters (35 inches).

Source: U.S. National Institutes of Health (NIH)

A related indicator is waist circumference divided by height. The values indicating increased risk are:

  • greater than 0.5 for people under 40 year of age.
  • 0.5 to 0.6 for people aged 40–50.
  • greater than 0.6 for people over 50 years of age.
All this is good but I am too lazy to do so much of calculations

If you are looking for an easy way to accurately measure your weight and body fat, I recommend the below tools. These body fat analyzers may not be 100% accurate. But as long as you use the same scale, you will be able to determine if you losing fat or not.

Body Fat Analyzers

Below are the top most rated weighing Scale on Amazon. These scales also estimate your muscle mass along with your biometrics like BMI and bone density. The best part is that the scales will automatically sync with your phone.

RENPHO Bluetooth Body Fat Scale

1byone Bluetooth Body Fat Scale

If you are looking for something more comprehensive that lets you track more than just weight and body fat, I recommend Nokia Body+ or Nokia Body Cardio.

Nokia Body+

  • It completely analyzes your body fat, water percentage, muscle and bone mass.
  • You can track weight and complete body composition for your entire family.
  • It also helps you track your calorie and nutrition.
  • You can set a goal and manage your calorie budget through its companion app – Health Mate. This app is available for both iPhone and Android.

Nokia Body+ is my personal favorite. I use it daily to track my and family’s health and fitness.

Nokia Body Cardio does everything that Nokia Body+ does and it also tracks your heart rate.

At the end, there is no single method for you to determine your ideal body weight. Your ideal body weight should be a weight where your body fat is is not too high or too less. For instance my BMI is 21, body fat % is between 10-12%. This is a good BMI & body fat% for men to be in.

Let me know, what is your BMI is and what step you will take today to become a healthier version of yourself?


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